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Four and a half months after a devastating explosion destroyed a $200 million dollar satellite and much of its Cape Canaveral launch complex, a SpaceX Falcon 9 blasted into space today on an all-important return-to-flight mission that successfully deployed the first 10 of Iridium’s next generation communications satellites to low Earth orbit.

Flying from Space Launch Complex 4-East at Vandenber AFB in California, the Falcon lifted off the pad at 9:54:39 a.m. PST and quickly soared into a cloudless blue sky as it raced southward on the high-inclination trajectory required by the Iridium NEXT 1-10 satellites.

After the first stage’s nine Merlin 1D engines burned out and the Falcon upper stage separated and took over the remainder of ascent to orbit, the first stage guided itself back to Earth to make a pinpoint landing on an autonomous drone ship stationed in the Pacific Ocean. Touchdown on the ship, dubbed “Just Read The Instructions”, marked the first successful Falcon landing on the West Coast. The previous six landings all occurred at Cape Canaveral’s Landing Zone one or on the droneship “Of Course I Still Love You”.

Falcon 9 on recovery ship. Credit: SpaceX webcast.

Meanwhile, the single Merlin 1D on the second stage burned for another six and a half minutes before it shut down after reaching a preliminary parking orbit. The stage and spacecraft coasted until T+52 minutes, when it restarted its engine for a brief 3-second burn.

Then began an intricate 15-minute deployment sequence, at times in radio blackout, to release all 10 satellites into polar orbit 388 miles high.

Credit: SpaceX

Iridium NEXT will replace the world’s largest commercial satellite network of low-earth orbit satellites in what will be one of the largest “tech upgrades” in history. When it’s complete the Iridium NEXT constellation will include 70 spacecraft with a 12.5 years design life, on-orbit spares, and ground backup spacecraft. The network will be used for the company’s satellite phone services, messaging and aircraft and ship tracking.

Each 860 kg spacecraft employs an L-band phased array antenna for generation of the 48-beam, 4,700 kilometer diameter cellular pattern on the Earth’s surface for communication with subscribers/users. Ka-band links are also provided for communications with ground-based gateways and for crosslinks with adjacent spacecraft in orbit.

The cross-linked satellite constellation forms a global network in space allowing communications from a ground or airborne user from any location on Earth to anywhere else on Earth.

The Iridium NEXT spacecraft design allows for up to a 54-kilogram hosted payload. Hosted payloads enjoy the interconnectivity of the Iridium network and near-real time relay of data to and from space, providing the end user global coverage at a fraction of the price of a dedicated mission. The end user receives hosted payload data via an IP interface to Iridium facilities, which obviates the need for any customer owned ground stations.

Iridium NEXT will enable the development of new and innovative products and solutions across Iridium’s vast partner ecosystem. Additionally, Iridium Certus, the next-generation multi-service communications platform enabled by Iridium NEXT, will deliver faster speeds and higher throughputs across multiple industry verticals.

While the primary objective of the mission was to deploy the ten Iridium satellites, it was equally important for SpaceX to return the Falcon 9 to flight status following the mishap on September 1 that also destroyed the Amos 6 satellite. That setback put pressure on SpaceX to return to flying quickly and work off a growing backlog of customer launches. The company was already attempting to catch up following the failure of CRS-7 a year earlier when September’s anomaly occured.

Ramping up the flight rate is essential because SpaceX plans possibly 20 launches this year and crewed Dragon test flights in 2018, in addition to the debut of the Falcon Heavy vehicle.

Working with the FAA and NASA, investigators narrowed down the cause of the Amos 6 mishap to a dynamic interaction between the liquid helium composite overwrap pressure vessels (COPV) and the super-chilled densified oxygen.

“[T]he investigation team concluded the failure was likely due to the accumulation of oxygen between the COPV liner and overwrap in a void or a buckle in the liner, leading to ignition and the subsequent failure of the COPV,” SpaceX said in a statement on January 2.

“Each stage of Falcon 9 uses COPVs to store cold helium which is used to maintain tank pressure, and each COPV consists of an aluminum inner liner with a carbon overwrap. The recovered COPVs showed buckles in their liners. Although buckles were not shown to burst a COPV on their own, investigators concluded that super chilled LOX can pool in these buckles under the overwrap. When pressurized, oxygen pooled in this buckle can become trapped; in turn, breaking fibers or friction can ignite the oxygen in the overwrap, causing the COPV to fail.”

“In addition, investigators determined that the loading temperature of the helium was cold enough to create solid oxygen (SOX), which exacerbates the possibility of oxygen becoming trapped as well as the likelihood of friction ignition.”

Credit: SpaceX

With the Iridium NEXT mission successfully behind, SpaceX’s attention now turns to resuming flights from Florida. Space Launch Complex 40 requires extensive repairs and likely won’t be available for at least several more months. For comparison, after the Orbital ATK Antares failure at Wallops Island in October 2014, it took nearly a year to repair the launch pad.

With SLC-40 out of commission, employees have been working night and day to complete modifications to the former space shuttle launch pad,LC-39A, at Kennedy Space Center that SpaceX leased from NASA. This is the complex from where crewed Dragon and Falcon Heavy launches will take place, in addition to being capable of launching the Falcon 9.

Those modifications are nearly complete and the first flight from LC-39A since Atlantis blasted off on the final shuttle mission, STS-135, could take place as early as January 26 carrying the EchoStar23 commercial communications satellite.